A CA 19-9 level of 66 U/mL is mildly elevated (normal is typically under 37 U/mL). There is no specific medication to lower CA 19-9, as it is a biomarker, not a disease itself. This mild rise can be caused by non-cancerous conditions like gallstones, pancreatitis, or liver inflammation, as well as certain cancers. You should not start any medication without a proper diagnosis. Please consult your doctor or a gastroenterologist. They will evaluate your symptoms and likely recommend further tests, such as an abdominal ultrasound or CT scan, to find the underlying cause and prescribe the correct treatment.